A power outage should not cause that Relay to do anything one way or the other.
The only devices that are typically affected by a power outage are zigbee lightbulbs, which usually come on the full bright when power is restored. Everything else should be just where it was when the power went off.
If you have a phone which loses power and then comes back on power, that might trigger your “I’m home” events, but that’s a different kind of problem.
It could just be a coincidence, but other people have been reporting poltergeist events, including some garage doors opening, over the last couple of days:
Make sure you report it to support. They can check the logs and see what triggered the garage door.